05-09-2012, 04:47 PM
Open-WiSe: A Solar Powered Wireless Sensor Network Platform
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Abstract:
Because battery-powered nodes are required in wireless sensor networks and energy consumption represents an important design consideration, alternate energy sources are needed to provide more effective and optimal function. The main goal of this work is to present an energy harvesting wireless sensor network platform, the Open Wireless Sensor node (WiSe). The design and implementation of the solar powered wireless platform is described including the hardware architecture, firmware, and a POSIX Real-Time Kernel. A sleep and wake up strategy was implemented to prolong the lifetime of the wireless sensor network. This platform was developed as a tool for researchers investigating Wireless sensor network or system integrators.
Introduction
Today, wireless sensor nodes are key components of wireless sensor networks (WSNs), which, in themselves, have become an important field of study. WSNs have evolved significantly over the past decade in the areas of computing capacity, sensor resources, communication, energy storage, and cost.
Because WSNs require battery-powered nodes and energy consumption is a primary factor in the design of WSNs, alternate energy sources are needed to permit them to function more effectively and
OPEN ACCESS for longer periods of time. Solar energy has become more attractive recently because of its environmental benefits and because the efficiency of photovoltaic cells has increased significantly in the past few years. Solar energy is derived from Nature’s greatest renewable resource and it is non-toxic in nature. Solar cells can be utilized to power the sensor as well as to charge the batteries for WSNs [1], where their design goal is to provide autonomy lifetime (for wireless sensor nodes), making WSNs more valuable in terms of versatility and longevity.
Related Work
Research groups have developed various different platforms, some of which have very specific characteristics depending on application requirements. In [4] propose a hybrid wireless sensor networks architecture based on the Tmote sky and Fox board platform. Whereas in [5], probably the most well-known platform is the Mica series from UC Berkeley. In [3], the SENTIO platform is presented as a hardware platform for rapid prototyping of WSN. Both Mica and SENTIO have similar computational power and consume approximately the same power. However, unlike these, Open-WiSe has greater computational power and similar power consumption because it is designed for either novices or expert WSN designers.
Open-WiSe consumes approximately the same amount of power as Mica and SENTIO. It does so by disconnecting the Xbee wireless module and solely operating with the CC2420 radio. Furthermore, it also contains a solar charger module in the same PCB. Other recent platforms include Telos [6] from UC Berkeley and XYZ [7] from Yale University, which consume significantly less power than many conventional platforms.
Sleep-Wake up Strategies
Because a credible deployment of WSN is based on the energy management of sensor nodes and energy is a finite resource, different sleep and wake up polices can be used to prolong the WSN lifetime. We consider two variables (battery l and solar radiation r) in the sleep and wake up models. When the battery state is l and the solar radiation is r, the node can switch from the active to the sleep mode and vice versa. We use a random variable N to represent the mode of operation of the sensor.
Conclusions and Future Work
In this paper, we have presented a new solar powered model for the rapid prototyping of wireless sensor networks. The platform was developed as a tool for developers of WSN. One important feature of the Open-WiSe mote, among others, is the two 802.15.4 radios which allow developers to set up a rapid WSN application. Other important features of the WiSe mote include its robustness and low price. In addition, the schematics, gerber files, and PaRTiKle OS are available on the corresponding author’s personal web page .